The present invention relates generally to electromagnetic and particle beam radiation, and, more specifically, to transmission thereof in high vacuum.
Such radiation beams have many uses in various commercial industries, scientific studies, and experimental research. Radiation beams may be generated with substantial energy therein in various beam generators. The beam generators are typically operated under various levels of vacuum including high and ultra-high vacuum as required.
For example, the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory provides two evacuated storage rings with a substantial number of experimental stations thereat. Photon energy from 10 eV to 20 keV in the form of infrared light, ultraviolet light, and x-rays are available for use in experiments. Furthermore, the Advance Photon Source (APS) at the Argonne National Laboratory is also available for using x-rays in experiments. In both systems, the beams are circulated in corresponding storage rings which are evacuated to suitable levels of vacuum for maintaining the efficacy of the beam. The experimental or test stations are located at the end of corresponding beamlines or extraction tubes through which the beam is extracted for testing purposes.
The extraction tube includes several valves for isolating the test stations from the storage ring when required. During testing, the valves are open for permitting extraction of the beam while maintaining the normal level of vacuum in the storage ring.
However, in the event of any damage in the test station in which a vacuum leak occurs, the test station must be quickly isolated from the storage ring by closing one or more of the valves in the extraction tube to prevent loss of the normal vacuum in the storage ring.
This isolation must occur extremely rapidly, and is effected using mechanical valves in which a valve piece is rapidly driven to engage a cooperating valve seat and close the beamline path from the storage ring.
Due to inherent limitations of mechanical valves, the fastest valves for this use have a limited closure time typically on the order of a few milliseconds. And, this fast closing time typically results in damage to the valve which then requires its repair prior to being reused.
Accordingly, it is desired to provide a fast-acting valve for use in closing a beamline under vacuum while permitting unobstructed beam travel when the valve is open.
A plasma valve includes a confinement channel and primary anode and cathode disposed therein. An ignition cathode is disposed adjacent the primary cathode. And, power supplies are joined to the cathodes and anode for rapidly igniting and maintaining a plasma in the channel for preventing leakage of atmospheric pressure through the channel.